Development of a quantum dot-based immunochromatography test strip for rapid screening of oxytetracycline and 4-epi-oxytetracycline in edible animal tissues.

A rapid and sensitive immunochromatographic test strip (ICTS) was developed in a competitive format with the quantum dot-conjugated monoclonal antibody specifically to determine the residues of oxytetracycline (OTC) and its metabolite 4-epi-oxytetracycline (4-epi-OTC). Using an ICTS reader, the 50% inhibition concentration (IC50) was found to be 3.41 +/- 0.29 ng ml(-1) of OTC in phosphate-buffered saline samples and the detection limit was 0.44 +/- 0.05 ng ml(-1). The visual cut-off level of the ICTS is 25 ng ml(-1). The recoveries from tissue samples spiked with OTC of 50-600 mu g kg(-1) were 74.2-107.2%, with coefficients of variation below 15%. The method was used to analyse incurred tissue samples, and there was good correlation (R-2 = 0.999) between the ICTS and high-performance liquid chromatography. These results indicate that ICTS is suitable for the rapid and quantitative detection of OTC and 4-epi-OTC residues in edible animal tissues.